Phenol Biodegradation Coupled With Chromium(Ⅵ)Reduction By Pseudomonas Sp. JF122and Its Environmental Implications

Phenol and chromium (Ⅵ) are often encountered together in environments including soil, sediment, surface and ground. The co-contamination of chromium (Ⅵ) and phenol poses severe threats to the environment since both phenol and chromium (Ⅵ) are dangerous pollutants, thus solutions for simultaneous removal the two pollutants would be of high value. The simultaneous removal of chromium (Ⅵ) and phenol by consortium of bacteria suggested that electron donors for chromium (Ⅵ)-reducing bacteria were intermediate products of phenol degradation by phenol-degrading bacteria, in those processes, phenol was the sole carbon and energy source for microbes and toxic chromium (Ⅵ) was reduced to comparatively less toxic Chromium (Ⅲ). However, few researchers have investigated the biodegradation of phenol with chromium (Ⅵ) reduction by a single bacterium. A bacterial isolated from natural ecosystems is expected to possess potential in bioremediation of pollution from contaminated environments. In this work,A bacterium capable of phenol biodegradation and chromium (Ⅵ) reduction was isolated, the effect of initial concentration of phenol and chromium (Ⅵ) on phenol biodegradation coupled with chromium (Ⅵ) reduction, the growth kinetics and the mechanisms for phenol degradation and chromium (Ⅵ) reduction were investigatedrespectively.A bacterium capable of phenol biodegradation was isolated and identified by using standard biochemical tests and morphology observationand16S rRNA sequence analysisas Pseudomonas sp. JF122.Biodegradation of phenol by Pseudomonas sp.JF122was affected by various factorssuch as inoculum size, glucose concentrations, cell density, agitation rate,salinity concentrations and heavy metals during incubation. The strain isolated was able to degrade800mg/Lphenol when it was incubated on a rotary shaker for60hours at30℃, pH of6.5and170rmp.The strain JF122capable of phenol biodegradation with Chromium (Ⅵ) reduction, the capacity of phenol degradation with Chromium (Ⅵ) reduction was affected by initial concentration of Chromium (Ⅵ), inoculum size and phenol concentration.The maximum Chromium (Ⅵ) reduction capacity of strain JF122in the presence of phenol concentration of600mg/L was2.0mg/L. Chromium (Ⅵ) was reduced to soluble Chromium (Ⅲ) kept in supernatant.The response surface methodology was used to establish mathematical model between JF122growth and the influence factors of temperature, initial pH and inoculation size. Furthermore, the growth conditions of JF122were also optimized. The results showed that the optimized growth condition for JF122was pH of6, inoculum size of0.95%and temperature of28.56℃.which was agreed with that of its phenol-degradation and chromate-reduction condition.The Haldane equation was used to study phenol biodegradation and Chromium (Ⅵ) reduction by JF122respectively. The Haldane constants of phenol biodegradation and Chromium (Ⅵ) reduction were derived by nonlinear regression using MATLAB software. The maximum specific growth rate for phenol degradation and chromium reduction0.3091and0.1126h-1respectivelyThe yield coefficient value of Chromium (Ⅵ) reduction and phenol biodegradation were169.21mg cell/mg Chromium (Ⅵ) and0.362mg cell/mg phenol, respectively.Further, the decay coefficients have been found to be0.0104h-1for the growth on phenol and0.0162h-1for the growth on phenol and Chromium (Ⅵ).The novelty of this dissertation is the biodegradation of phenol coupled with Chromium(Ⅵ) reduction performed by a bacterial strain,which has important academic and practical significance.